Propagation and conservation of Podophyllum hexandrum Royle: an important medicinal herb

Podophyllum hexandrum Royle, a source of highly valued podophyllotoxin, has been subjected to heavy collection from the wilds due to ever increasing demand. This report deals with the successful propagation of this species using both conventional and in vitro techniques. To improve vegetative multiplication, rhizome segments were treated with alpha-naphthaleneacetic acid (NAA) or indole-3-butyric acid (IBA) before planting; more than doubling in rooting percentage was observed with 100.0 mu M IBA. Seed germination generally started 3 months after sowing, and pre-treatment with sodium hypochlorite resulted in five-fold improvement, while 250.0 mu M gibberellic acid (GA(3)) and a combination of GA(3) and 6-benzyladenine (BA; 250.0 mu M each) enhanced germination by nearly two-fold; other treatments were either ineffective or enhanced germination only marginally. Excised zygotic embryos germinated within 7-8 days of culture on basal medium or on medium supplemented with indole-3-acetic acid (IAA; 1.0-4.0 mu M) and BA (1.0 mu M). Multiple shoots were formed within 4-5 weeks; following rooting of these shoots, plants were transferred to hardening pots. Somatic embryos were formed from callus derived from zygotic embryos after 4 months of culture on medium containing 5.0 mu M NAA and 0.5 mu M BA. Various strategies have been discussed to encourage cultivation of this medicinal herb so as to reduce pressure on its population in the wild. (C) 1999 Elsevier Science Ltd. All rights reserved.